1. Field of the Invention
The present invention relates to a DC power control circuit suitable more especially, but not exclusively, for controlling and/or supplying the power circuits of automatic devices.
2. Description of the Prior Art
Generally, it is known that circuits of this kind already exist equipped, for example, in the way described in patent FR No. 2 254 136, with a protection device comprising an AND gate one input of which receives the control signal and the output of which controls an output amplifier. In this example, the output circuit of this amplifier comprises a current limiting means followed by a current sensing means. The voltage taken from the terminals of this current sensing means is applied to a threshold comparator which controls a flip-flop.
When this flip-flop has switched through detection of an overcurrent, it transmits pulses generated by a clock to the other input of the AND gate, which causes chopping of the output current, so reducing it to a mean acceptable value during the existence of the overload.
Such a device has the following drawbacks:
operation of the limiter corresponds to a disturbance which causes non execution or partial execution of the logic signal received by the protected output without the control logic being informed of these defects in executing the order received; PA1 other reasons, such as a defect in the power supply or in the output amplifier, may cause non execution of the logic order received without the control logic being informed.
Such incoherences between the logic state and the physical state of the members of an automatic device may have serious consequences which place the automated system and even the persons in the vicinity in danger if no device allows these incoherences to be detected and taken into account so as to avoid dangerous operating modes.